The summit of the 10-member Association of Southeast Asian Nations (ASEAN) and six dialogue partners -- China, Japan, South Korea, India, Australia and New Zealand -- takes place in the coastal resort of Hua Hin on October 23-25.

Supporters of ousted Thai premier Thaksin Shinawatra, known as the "Red Shirts", stormed the last summit in the beach town of Pattaya in April, forcing some regional leaders to flee the venue in helicopters.

The meeting had been postponed from December and moved out of its original location in Bangkok after rival demonstrators from the anti-Thaksin "Yellow Shirt" movement blockaded the capital's airports.

Intent on preventing a repeat of the embarrassing chaos, Thailand -- which remains deeply politically divided -- is invoking heavy security measures at the upcoming summit, including a harsh internal security law.

"There will be combined forces of 18,298 -- of these 5,000 are from the army, 4,000 are from police forces and the rest will be navy and air force officers," government spokesman Panitan Wattanayagorn told reporters.

"No demonstrations will be allowed in the area where the Internal Security Act (ISA) is being invoked. The prime minister has asked everybody concerned to work at their best to restore normalcy to Thailand," Panitan said.

While the Red Shirts have not yet indicated whether they will target the summit, it is considered unlikely as Hua Hin is the site of one of the main palaces of Thailand's widely revered king.

But Panitan said they had received intelligence reports that some other groups, such as environmental activists, could be planning rallies during the meeting.

In July, Thailand invoked the ISA at the ASEAN Regional Forum in the resort island of Phuket, attended by US Secretary of State Hillary Clinton. It passed off without riots.